1. Field of the Invention
This invention relates to a method and apparatus for increasing Vitamin D content in a mushroom slurry comprising a fluid, such as water, and fresh mushrooms, or mushroom parts, spawn and/or mycelia. The slurry is exposed to a broad spectrum of light for a specified period of time, using an electric glow discharge lamp. The slurry then is filtered to remove excess water and undesirable soluble materials. The remaining filter cake is dried and ground into a powder. The resulting mushroom powder has high levels of Vitamin D2, and is all natural, vegetarian, and can be used as an ingredient to fortify foods.
2. Description of the Prior Art
The two major forms of Vitamin D are Vitamin D2 and D3. Vitamin D2 is not produced by the human body and is only derived from fungi and plant sources. Vitamin D3 is produced in human skin through exposure to sunlight. The benefits of Vitamin D are numerous, and deficiency of the vitamin in humans can lead to several diseases. Because human exposure to sunlight for prolonged periods is impractical, in order to receive the benefits and overcome potential deficiencies of Vitamin D, there is a need for a method and an apparatus to increase Vitamin D2 in mushrooms and in dried mushroom powder to create a foodsource for this important vitamin.
Commercially grown mushrooms contain very low levels of Vitamin D2, typically less than 20 International Units (IU) per 85 gram standard fresh serving. 40 IU of Vitamin D2 equals 1 microgram. Mushrooms, however, naturally contain ergosterol, a biological precursor to Vitamin D2. Research shows that ergosterol in several species of mushrooms converts to Vitamin D2 when exposed to UV light. White button mushrooms, brown portobello mushrooms, shiitake mushrooms, and oyster mushrooms are some types of mushrooms known to show a Vitamin D2 response when exposed to UV light. With sufficient duration and exposure, the level of Vitamin D2 in these and other mushroom species can reach or exceed 400 IU/85 g of fresh mushrooms, equating to 100% of the current recommended Daily Value for Vitamin D in the United States.
To increase Vitamin D level in mushrooms, certain methods in the background art require mushroom exposure to UV light for extended periods to achieve a significant increase in the level of Vitamin D. In one method, exposure times from 1 hour to 24 hours were required. In other methods, 20 minutes to 60 minutes of exposure time were required. See Jasinghe, V. J., Perera, C. O., “Distribution of ergosterol in different tissues of mushrooms and its effect on the conversion of ergosterol to vitamin D2 by UV irradiation,” Food Chem. (2005), 92, pp. 541-46; Jasinghe, V. J., Perera, C. O., “UV irradiation: The generator of Vitamin D2 in edible mushrooms,” Food Chem. (2006), 95, pp. 638-43; and Jasinghe, V. J. “Conversion of ergosterol in edible mushrooms to Vitamin D2 by UV radiation,” Thesis submitted to the Department of Chemistry, National University of Singapore (2005).
The prior work to increase Vitamin D content in mushrooms relates to treating fresh mushrooms with UV light. Photolytic treatment of dried mushroom powder to produce high levels of Vitamin D2 has also been taught. Alternative methods for treating commercially viable quantities of mushrooms for short treatment times to produce foods or food additives with high Vitamin D2 content continue to be sought.